Air volume regulator for stokers



Sept. 9, 1952 J. A. WILSON ET AL 2,609,834

AIR VOLUME REGULATOR FOR STOKERS Filed June 26, 1946 i: SHEETSPSHEET 1INVENTORS John A.Wllson John HAROLD HANSEN UM y 7% ATTORNEYS p 1952 J.A. WILSON ET AL 2,609,834

AIR VOLUMEIREGULATOR FOR STOKERS 2 SHEETS-SHEET 2 Filed June 26, 1946INVENTOR.S John 'A wllson 3' BY ohn HAROLD Hansen ATTORNEYS PatentedSept. 9, 1952 UNITED STATES PATENT OFFICE AIR. VOLUME REGULATOR FORSTOKERS John A. Wilson and John Harold Hansen, Detroit, Mich., assignorsto The Timken-Detroit Axle Company, Detroit, Mich, a corporation of OhioApplication June 26, 1946, Serial No. 679,520

. 9 C a ms- I i This invention relates generally to fuel stokers andmore specifically to meansfor automatically controlling the supplyofcombustion air to the fuel bed in such .stokers.

In stokers of conventional construction the fuel is fed from thehoppertothe retort at a constant rate and combustion air, is supplied tothe retort through aseparate duct coupled to the outlet of a constantspeed blower. Experience has shown. that changing conditions ,at thefuel bed, such as the thickness andfirmness oflthe bed, the presence ofblow holes or thin spots. alteration in the character of the coal, etc,all contribute to uncontrollable variation of the delivered combustion,air Pressure and hence permit such variations in the volume ofcombustion air supplied to the retort per unit time as to render burningcumulatively inefficient. It hastherefore been found necessary tocontrol the rate of combustion air delivery to the retort to maintainthat rate asnear constant as possibleto the rate which will provide mostefficient .fueltcombustion for the burner. I

Air volume regulators with dampers which are initially manuallyadjustable to .a fixed position and capable of modifying the output ofthe blower fajn have been proposed but these will deliver therequiredvolume .of air only at a given static pressure, so that as thestaticpressure at the fuel bed varies due to the above mentionedchanging conditions, the volume of air delivered will, also .varyuncontrollably. Hence automatic air volume controls have been foundnecessary and some have been proposed and used, l

Automatic .air volume regulators now available have succeeded somewhatin controlling the volume. of air delivered to compensate for thevarying static pressure at the fuel bed. These earlier regulatorsgenerally actuate a damper in the air duct either in response to apressure drop measuring. device or a velocity responsive element in the:path. of the combustion air. Although many of these knownregulatorshave been considered eflicient, inugeneraltheir. complicatedstructure renders them undesirable from a cost standpoint.

. In the present invention we have devised an automatic air volumeregulator. which is of simplified construction and more eificient inoperation than said earlier more complicated regulators.

. Our present invention in its preferred embodiment difi'ers from allother automatic air volume regulators known to us inasmuch as itembodies a novelrotary damper or shutter in the combustion air ductadjustable to anormallyopen position which determines the maximum rateof air flow through the duct. A stabilizer is provided for the damper torestrain its rotation in response to sudden variations in velocity ofair flow due to'sudden pressure changes, thus dampening the damperagainst undesirable fluctuation. l

The major object of the invention istherefore to provide a novelautomatic air volume regulator of simple construction whichwill insure auniform and constant volumeof air flowing through an air duct to thefuel bed of a burner, regardless of the resistance to air flow offeredby the fuel bed.

A further object of thisinvention is to provide a novel rotary airvolume regulator for the control of air iiow in a stroker or the like. Y

Another object of the invention is to provide a novel air volumeregulator valve having. .a statically balanced rotor equipped with aninertia member which is adjustable for varying the normal open positionof the rotor and which is arranged for counteracting the effect of theair flow tending to close said valve.

A further object of this invention is to provide a novel stabilizingarrangement for a :rotor damper in a stoker or the like.

It is a further object of the invention to provide a novel air volumeregulator rotor adapted to be disposed in a. combustion air stream andwhich is not of itself afiected by the air velocity regardless of itsadjusted position.

A further object of the invention is to provide a novel balancedquadrant type rotor valve for an air volume regulator.

A further object of the invention is to provide a novel air volumeregulator having a rotary valve element which is statically balanced andadapted to rotate in response to velocity changes in combustion air flowtherethrough, and adjustable means for opposing said tendency to rotatedue to air iiow and for determining the maximum opening of said valve.

Still another object of this invention is to provide an air volumeregulator having a rotor equipped with a novel blade or said arrangementfor insuring that the rotor is responsiveto air flow during its entirerange of movement;

A still further object of the invention is to provide a rotary airvolume regulator valve having a novel inertia member mounting arm fixedon the rotor shaft.

Other objects of the invention will become 3 apparent as the descriptionproceeds in connection with the appended claims and the annexed drawingswherein:

Figure l is a top plan view of a coal stoker assembly partly broken awayto illustrate an air volume control according to a preferred embodimentof the invention;

Figure 2 is a side elevation of the stoker of Figure 1 also broken awayto illustrate the air volume control in the assembly;

Figure 3 is an enlarged side elevation of the air volume regulator apartfrom the rest of the stoker; V

Figure 4 is a transverse section through the air flow regulatorsubstantially along line 44 of Fig-' ure 3;

Figure 5 is a partial longitudinal section through the air flowregulator substantially along line 5--5 of Figure 4;

Figure 6' is an end elevation of the rotor element of the air volumeregulator illustrating the blade or sail arrangements; and

Figure '7 is a section along a diameter of rotor damper stabilizer.

The stoker assembly comprises an open topped cabinet containing a hopperl2 open at its bottom to a channel |3 in which is disposed a feed screwl4. Feed screw I4 is driven through transmission [5 by an electric motorl3 within the cabinet and extends through a tube 11 to a suitable retort|8 located at the furnace. Coal delivered into hopper I2 will thus becontinuously fed to retort 8 when motor I5 is operating. Cabinet H isclosed at the top by a suitable operable cover i9.

Motor shaft 2| is drive connected to the fan of a suitable constantspeed and constant output blower 22, and the outlet of blower 22 isconnected to a conduit 23 which extends generally parallel to tube l1and delivers combustion air from the blower to retort Hi. This generalassembly is conventional in coal burner stokers.

an air volume regulator 24 is interposed in the combustion air passagebetween blower 22 and conduit 23', and preferably comprises a sheetmetal duct 25, generally rectangular in cross-section and providedsubstantially at its center with a part cylindrical portion 25 havingits axi horizontal and normal to the longitudinal axis of the duct.

Duct 25 comprises a top'panel 21 anda bottom panel '23 both secured asby welding along adjacent edges to a rear panel 29, and a front panel isdetachably secured along its edges to the top and bottom panels bysuitable fastener assemblies 3|.

As illustrated in Figure 4, panels 23 and 33 are formed with cylindricalpockets 32 and 33-at cylindrical portion 26 of the duct, for housing theends of a damper rotor to be described. As illustrated in Figure 5, toppanel 21 is formed at cylindrical portion 26 of the duct with anoutwardly projecting cylindrical wall 34, and lower panel 28 issimilarly formed with an outwardly projecting cylindrical wall 35. Walls34 and 35 are equal in size and extend for quadrants of the cylinder,the other two quadrants of the cylinder being open'to duct 25.

I A suitable damper member 36 is mounted for rotation within cylindricalportion 26 of the duct and it preferably comprises a cylindrical rotormounted for free rotation on a horizontal axis. Rotor 36 comprises twoparallel flanged side discs 31 and 38 secured along their edges as bywelding to a lower part-cylindrical plate 39 and an upperpart-cylindrical plate 48. The cylindri- 4 cal surface of the rotor 36is thu divided into two closure portions, an inlet aperture 4| and anoutlet aperture 42. The width of apertures 4| and 42 is equal to thewidth of duct 25 opening thereinto.

Lower plate 39 is preferably a quadrant in extent and upper plate 40 isalso substantially a quadrant in extent so that, when the rotor isdisposed as illustrated in Figure-5, duct 25 will be substantiallyunobstructed by the rotor in that closure plates 39 and 48 are disposedentirely out of the air flow path. As illustrated in Figure 4, the sides31 and 38 of rotor 36 are substantially coplanar with panels 33 and 29so that apertures 4| and 42 are of substantially the same size as duct25.

Rotor 36 is secured non-rotatably upon a horizontal shaft 43. Preferablyshaft 43 is square and extends through square apertures in discs 31 and38, which are retained from lateral movement on the shaft, as by beingstaked to the shaft at 44 and 45. Shaft 43 extends through a clearanceaperture 46 in front panel 30 and is journalled at one end on a conicalpointed screw 41 which is adjustably mounted in a suitably threadedaperture of an outstanding U-shaped bracket 48 secured as by welding tofront panel 30. Screw 41 when adjusted is locked by jam nut 49. The rearend of shaft 43 is journalled on a similar conical pointed screw 5|adjustably mounted in a suitable threaded aperture in a lug 52 securedas by welding to rear panel 29. Screw 5| is locked in adjusted positionby jam nut 53. This mounting of shaft 43 provides for lateral adjustmentof rotor 38 with respect to the path of airflow so that apertures 4| and42 may be accurately centered and aligned with the duct.

Shaft 43 and-rotor 35 are therefore mounted for rotation insubstantiallyfrictionless bearing supports which provide for instant response of therotor to forces tending to rotate it.

The rotor has been described in a high degree of particularity becauseit is considered to be an important feature of this invention, it havingbeen discovered that this element may be rotated to any given angularposition within an air duct and maintain that position functioning a avalve to govern the volume of air and maintaining its position withoutbeng materially affected bythe velocity of the air stream.

Outside the duct, an inertia member arm 55 is secured non-rotatably toshaft 43 between panel 30 and bracket 48 as by square apertures in itsU-shaped extremity fitting over square sides of shaft 43 and is retainedfrom lateral movement by set screw 56. Inertia member arm 55 consists ofa metal strap provided with an elonagted olfset slot 51 in which aninertia member or weight 58 is slidably mounted and locked by adjustingscrew assembly 59. When inertia member 58 is locked at the extremity ofarm 55' farthest from the axis of rotor 36, the center of gravity of theentire rotor and inertia member assembly mounted on bearings 41 and 5|is so located as to dispose the rotor in the position illustrated inFigure 5 whereby the duct is completely unobstructed by closure plates39 and 49.

Slot 51 runs at such angle and is offset such a distance that wheninertia member 58 is adjusted toward the axis of rotor 36 the center ofgravity of the entire assembly is shifted to tend to rotate rotor 36clockwise from the position of Figure 5 and thereby restrict the flow ofcombustion air through duct 25. The position of weight 58 thereforedetermines the maximum normalidle opening of the duct, as will furtherappear. l

A rotorstabilizer 6| is provided on shaft 43 outside front panel 38-Stabilizer 6| preferably comprises an annular casing 62 made of twoidentical cups secured together as by bolt assemblies 63. Casing 62 isjournalled on the cylindrical hub 64 of a stabilizer disc 65 which isnon-rotatably secured upon shaft 43 so as to rotate therewith. Casing 62is anchored against rotation, as by a pin 66 on panel38 projectingthrough an aperture in peripheral flange 61 of the case.

Stabilizer disc 65 operates in a chamber 68 which is preferably filledwith a viscous grease that has the same consistency from forty degreesbelow to two hundred degrees above zero centigrade. The grease adheresto the relatively rotatable surfaces of stationary case 82 andstabilizer disc 65, thereby tending to retard and dampen any suddenchanges of position between the case and disc. Rotor 36 is thusrestrained from oscillating in a fluctuating air current due to suddenlyvarying resistances of the fuel bed and the pull of the chimney draft.

A plurality of transverse sails or vanes 69, 10 and 1| are providedextending across aperture 4| in the path of the incoming combustion-air.These vanes are each arcuate sheet metal plates, preferably welded attheir ends to rotor discs 31 and 38. As illustrated in Figure 5, theseveral vanes are so disposed that air entering as indicated by thearrow will tend to rotate rotor 36 clockwise. The purpose of thisarrangement is to insure that substantially the same eifective area ofthe vanes is presented normal to the incoming air stream during theentire range of rotation of rotor 36 so that the .air stream through theduct at all times retains control of the rotor.

i In operation, the combustion air supplied by blower 22 isautomatically metered by regulator With no air passing through duct .25,as when blower 22 is inactive, the duct opening afforded by rotor 36depends upon the adjusted position of Weight 58 on arm 55, since whenthe rotor is idle and not under the influence of air velocity within theduct, the rotor assembly always tends to assume a position where weight58 is in the vertical plane containing the axis of rotation of theassembly. Thus,.starting with the maximum opening when weight 58 is inits outer-most position as in Figure 5, the idleopen position of therotor may be adjusted clockwise by adjustment of weight 58 upwardlyalong arm 55. This adjusted idle position of course determines themaximum effective duct opening for that adjustment.

When blower 22 is furnishing combustion air,

theforce exerted by the air stream against the rotor vanes tends torotate rotor 36 clockwise toward closed position and thus move closureplate 39 to restrict the effective opening in duct 25. Rotation of rotor36 is opposed by the countereif'ect of theinertia member which tends bygravityto return to its idle position.

The vertical distance that weight 58 is lifted per degree of rotation ofthe rotor is increased in harmonic proportion as arm 55 swings from thenormally idle hanging position toward a hori -zontal position when rotor36 is rotated by the air stream. Therefore, fora certain velocity of airin the duct, weight 58-will be lifted only through a certain number ofdegrees before the harmonic increasing opposition to such lift equalsthe lifting force due to velocity of the air stream, and the tendency ofthe air velocity to 010561130601 36 and the tendency of weight 58 toopen the rotor reach apoint of equipoise and rotor 36 is thereforemaintained balanced in an intermediate partly open position. where acertain air volume is delivered to the retort. X

Since it is usually known what volume 0 air per unit time affords mosteflicient combustion fora particular burner, itis apparentlthat theparts can readily be so proportioned and adjusted that rotor 36 assumesthe proper angular position to pass this air volume when blower 22 isoperating and the fuel bed conditions .are normal. 3

The amount that the rotor 36 will close due toa given velocity of airthrough the duct is dependent upon the adjusted position of inertiamember 58 on arm 55. When the inertia member is adjusted to a positionat the outer extremity of the arm as in Figure 5, the tendency ofinertia member 58 to hold the rotor open is rendered the most effectivepossible, since the leverage afforded by arm 55 is the greatestpossibleand inertia member 58 mustalso be moved through" ninety degrees ofrotation to completely close the rotor. As inertiamember 58is adjustedtoward the axis of rotation of arm 55, the rotor 36 is partially closedand thus neither it nor the inertia member will have to be liftedthrough degrees to close the rotor. Also inertia member 58 is renderedless effective due to the decrease inleverage afforded by arm 55. Inthepreferred embodiment of the invention .upper plate 40 is of slightlyless peripheral length than the lower plate 39 in order. that it maydeflect the air stream towards the vanes 69, 18 and H thereby insuring asubstantial amount of airagainst the vanes even when the duct 25may besubstantially closed by plate 39. i

In practice we prefer .to provide the rotor, veins and arm assembly,apart from weight 58, as a statically balanced assembly which willmaintain any given angular position of rotation in which it may beplaced, when blower 22 is not operating. Addition of the weight causesthe assembly to assume its normally open idle position from which it is,during operation, displaced to a balanced open position by velocity ofthe air stream through the duct. It will be appreciated that rotor 36 inpractice willprobably never completely shll off passage of air throughthe duct. i

Theeifect that the momentum of inertia member 58 would have in hinderingthe establishment of a point of balance for rotor 36 is cancelled out bystabilizer 84. The grease adhering to the surfaces of disc 92 and ofcase 86 retards the effect any force might have in tending to change theposition of the said disc within the said housing.

The offset construction of arm 55 is 'for the purpose of increasing ordecreasing the degree of maximum opening and obtaining a large effectiveleverage for weight 58through the use of a relatively short arm. Ifdesireclyarm 55 and weight 58 may be replaced by a spring assembly orany other suitable device to accomplish these same ends. 1

During normal operation when there are no unusual changes in the fuelbed'or effective draft in the burner, the normal balanced open positionof rotor 36 will be maintained. However, suppose that the fuel bedbecomes thicker and more resistive to traverse of combustion air, aswhen the coal feed is too high for efficient combustion of all the coal;Blower 22 keeps delivering a'constant volume of combusion air per unittime into the duct, but the thickened fuel bed resists its passage anddevelops an increasing back, pressure in the duct and an accompanyingreduction in velocity of the air passing through the duct. However,since the degree of closure effected by rotor 36 varies inversely withrespect to the air stream velocity, this reduction in air velocity willresult in a reduction of the closing force acting on the rotor andweight 58 will be permitted to rotate the rotorv counterclockwise toincrease the effective opening through the duct. This permits morecombustion air to ,be supplied to the fuel bed with the result that thefuel is burned faster and the tendency of the fuel bed to resist passageof air is now reduced. As the resistance of the fuel bed decreases,velocity of the air stream in the duct increases and the rotor starts torotate toward closed position. This continues until a normal fuel bedcondition is attained, at which time the rotor has regained its balancedopen position. The stabilizer 6| prevents sudden and merely temporarychanges in air stream velocity from affecting the rotor, but may not benecessary'for many installations.

Suppose that the fuel bed becomesthin and contains holes. The combustionair, since the back pressure in the duct is low, passes through the fuelbed at a relatively high velocity and tends to blow out the fire andscatter and deposit fly ash over the heating surfaces of the furnace. Inthe regulator of the invention, the high air stream velocity causesclockwise movement of rotor 36 toward closed position, thereby reducingthe volume of air supplied to the fuel bed, reducing combustion andenabling the coal feed to thicken up the fuel bed and reduce the airstream velocity. As the air stream velocity reduces, rotor 36 movestoward open position and a point of balance is gradually attained wherethe desired volume of air is being supplied to a normal fuel bed.

Our air volume regulator is eflicient in operation and inexpensive toconstruct and service, and is reliable.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

We claim:

1. In an automatic air volume regulator adapted to be interposed in apassage between a blower for supplying combustion air and a fuel burner,a statically balanced rotary valve member mounted for free rotation insaid passage on an axis transverse to the path of combustion air, saidmember havingopposed peripheral apertures adapted to be aligned withsaid passage anda passage closure portion adapted to move trans.-versely of the passage with rotation of said valve member, a transverseair impingement vane on said member extending across one of saidapertures, and means for opposing rotationof said member by said airstream.

2. A statically balanced shutter for an automatic air volume regulatorcomprising a rotary cylindrical member closed at its ends and providedwith diametrically opposite combustion air inlet and outlet apertures onits periphery, and transverse vane means secured to the periphery ofsaidmember in one of saidapertures.

3. In an automatic air volume regulator for a fuel burner having acombustion air passage connected to a source of air pressure, anenlarged region in said passage of substantially cylindrical shape, acylindrical shutter member rotatably mounted upon a transverse axiswithin said region, said member being provided with diametricallyopposite inlet and outlet apertures on its periphery and said apertureseach having a width and circumferential extent at least equal to theadjacent dimension of said passage so that member may be disposed withsaid apertures in substantially unobstructing alignment with saidpassage and with the peripheral wall of said, member disposed in saidenlarged region out of the combustion air path, vane means on saidmember in one of said apertures for rotating said member by the airstream through said passage, and means operatively connected to saidmember for opposing rotation thereof by the air stream.

4. In the automatic air volume regulator defined in claim 3, theperiphery of said member serving as a closure for said passage as saidmember is rotated.

5. In the automatic air volume regulator defined in claim 3, one of thetwo spaced peripheral wall portions of said member being of greatercircumferential extent than the other.

6. In an automatic air volume regulator having a passage adaptedtoconducta stream of air under pressure, means for automaticallycontrolling the amount of air delivered through said passage comprisinga valve rotor assembly and control means operably connected to saidvalve rotor assembly for opposing rotation of said valve rotor assemblyby the air stream, said rotor assembly including a valve rotor mountedfor free rotation in said passage about an axis that extendstransversely of said passage and disposed in the path of the air stream,and said valve rotor assembly having such balanced structure and weightdistribution that it is capable of maintaining any given position ofrotation of said rotor in said passageIwhen no air is being forcedthrough said passage, and means on said rotor in the path of the airstream for providing rotation o'fsaid rotor assembly in response to thevelocity of the airstream, the opposing forces of said air streamvelocity and said control means being balanced when said valve rotorassembly is disposed to permit passage of a substantially constantpredetermined volume of air through said passage. 7

7. In an automatic air volume regulator having a passage through whichair is adapted to be forced under pressure, a rotor assembly freelyrotatably mounted upon an axistransversely of said passage, a closuremember onsaid rotor assembly adapted to be progressively interposed inthe path of vthe air stream as'said rotor assembly is rotated inresponse tochanging velocities of said air stream, vane means on saidrotor assemblydisposed in the air stream for rendering said rotorassembly responsive to ve locity of the air stream, said vanemeanscomprising a plurality of blades so relatively disposed as to presentsubstantially the same total projected area to said air stream duringthe normal range of movement of said rotor assembly, and means foropposing rotation of said rotor assembly by the air stream.

8. In an air volume regulator, a rotor assembly including a rotor havingaligned peripheral apertures each substantially a quadrant in extent,air passage defining means in which said rotor is pivoted about asubstantially centroidal axis transverse to said passage and meansresponsive to the velocity of air flow through said passage tending torotate said rotor about its pivot so as to increase or decrease thepassage opening upon decrease or increase in said air velocity,respectively, and means operably connected to said rotor assemblyadjustable for determining the angular position of said rotor and themaximum opening of said passage through said rotor when air is passingtherethrough, said means also tending to maintain said rotor in its saidadjusted angular position.

9. In an air volume regulator, means defining a passage through whichair is adapted to be forced under pressure, a rotor assembly including avalve rotor, a transverse shaft in said passage for mounting said rotorfor angular movement about a substantially centroidal axis, said rotorhaving opposed peripheral apertures 10 each substantially a quadrant inextent, a vane on said rotor rendering the rotor responsive to airvelocity through said passage, an arm secured to said shaft having aportion offset with respect to a radius of said shaft, and means on saidarm adjustable for determining the angular position of said rotor andthe maximum opening of said valve when air is passing there'- through.

JOHN A. WILSON. JOHN HAROLD HANSEN.

REFERENCES CITED The following references are of record in the is ofthis patent:

UNITED STATES PATENTS Number Name Date 1,124,575 Zimmer Jan. 12, 19151,127,644 Kramer Feb. 9, 1915 1,898,244 Dodlill Feb. 21, 1933 2,010,694Jones Aug. 6, 1935 2,067,932 Kretzschmar Jan. 19, 1937 2,088,023 BaerJuly 27, 1937 2,232,981 Swanson Feb. 25, 1941

